Administration Of Oral Poliovirus Vaccine Research Articles

Estimation of oral poliovirus vaccine effectiveness in Afghanistan, 2010–2020

BackgroundAfghanistan is one of two countries with endemic wild poliovirus type 1 (WPV1). The oral poliovirus vaccine (OPV) is the predominant vaccine used for polio eradication. Although OPV has been administered in routine childhood immunization and during frequent supplementary immunization activities, WPV1 continues to circulate in Afghanistan and case incidence has been increasing since 2017. We estimated the effectiveness of OPV in Afghanistan during 2010–2020. MethodsWe conducted a matched case-control analysis using acute flaccid paralysis (AFP) surveillance data from 29,370 children < 15 years with AFP onset between January 1, 2010 and December 31, 2020. We matched children with confirmed WPV1 (cases) with children with non-polio AFP (controls) by age at onset of paralysis (+/- 3 months), date of onset of paralysis (+/- 3 months), and province of residence, and compared their reported OPV vaccination history to estimate the effectiveness of OPV in preventing paralysis by WPV1 using conditional logistic regression. To account for changes in OPV formulations provided over the analysis period, we stratified the analysis based on dates of the global switch from trivalent OPV (tOPV) to bivalent OPV (bOPV) in April 2016. ResultsBetween January 1, 2010 and December 31, 2020, there were 329 WPV1 cases in Afghanistan. The per-dose estimated effectiveness of OPV against WPV1 was 19% (95% CI: 15%–22%) and of ≥ 7 doses was 94% (95% CI: 90%-97%). Before the global switch from tOPV to bOPV, the per-dose estimated effectiveness of OPV was 14% (95% CI: 11%-18%) and of ≥ 7 doses was 92% (95% CI: 85%-96%). After the switch, the per-dose estimated effectiveness of OPV against WPV1 was 32% (24%-39%) and of ≥ 7 doses was 96% (95% CI: 90%-99%). DiscussionOPV is highly effective in preventing paralysis by WPV1; these results indicate that continued WPV1 transmission in Afghanistan is due to failure to vaccinate, not failure of the vaccine. Although difficult to implement in parts of country, improving the administration of OPV in routine immunization and supplementary immunization activities will be critical for achieving polio eradication in Afghanistan.

A Health Economic Analysis for Oral Poliovirus Vaccine to Prevent COVID-19 in the United States.

COVID‐19 led to a recent high‐profile proposal to reintroduce oral poliovirus vaccine (OPV) in the United States (U.S.), initially in clinical trials, but potentially for widespread and repeated use. We explore logistical challenges related to U.S. OPV administration in 2020, review the literature related to nonspecific effects of OPV to induce innate immunity, and model the health and economic implications of the proposal. The costs of reintroducing a single OPV dose to 331 million Americans would exceed $4.4 billion. Giving a dose of bivalent OPV to the entire U.S. population would lead to an expected 40 identifiable cases of vaccine‐associated paralytic polio, with young Americans at the highest risk. Reintroducing any OPV use in the U.S. poses a risk of restarting transmission of OPV‐related viruses and could lead to new infections in immunocompromised individuals with B‐cell related primary immunodeficiencies that could lead to later cases of paralysis. Due to the lack of a currently licensed OPV in the U.S., the decision to administer OPV to Americans for nonspecific immunological effects would require purchasing limited global OPV supplies that could impact polio eradication efforts. Health economic modeling suggests no role for reintroducing OPV into the U.S. with respect to responding to COVID‐19. Countries that currently use OPV experience fundamentally different risks, costs, and benefits than the U.S. Successful global polio eradication will depend on sufficient OPV supplies, achieving and maintaining high OPV coverage in OPV‐using countries, and effective global OPV cessation and containment in all countries, including the U.S.

Polio vaccination coverage and seroprevalence of poliovirus antibodies after the introduction of inactivated poliovirus vaccines for routine immunization in Japan

In Japan, the oral poliovirus vaccine (OPV) was changed to 2 types of inactivated poliovirus vaccine (IPV), the standalone conventional IPV (cIPV) and the Sabin-derived IPV combined with diphtheria-tetanus-acellular pertussis vaccine (DTaP-sIPV), for routine immunization in 2012. We evaluated polio vaccination coverage and the seroprevalence of poliovirus antibodies using data from the National Epidemiological Surveillance of Vaccine-Preventable Diseases (NESVPD) from 2011 to 2015. Several years before the introduction of IPV in 2012, OPV administration for children was refused by some parents because of concerns about the risk of vaccine-associated paralytic poliomyelitis. Consequently, in children aged <1 years who were surveyed in 2011–2012, polio vaccination coverage (45.0–48.8%) and seropositivity rates for poliovirus (type 1: 51.7–65.9%, type 2: 48.3–53.7%, and type 3: 15.0–29.3%) were decreased compared to those surveyed in 2009. However, after IPV introduction, the vaccination coverage (95.5–100%) and seropositivity rates (type 1: 93.2–96.6%, type 2: 93.1–100%, and type 3: 88.6–93.9%) increased among children aged <1 years in 2013–2015. In particular, seropositivity rates and geometric mean titers (GMTs) for poliovirus type 3 in <5-year-old children who received 4 doses of IPV (98.5% and 247.4, respectively) were significantly higher than in those who received 2 doses of OPV (72.5% and 22.9, respectively). Furthermore, in <5-year-old children who received 4 doses of either DTaP-sIPV or cIPV, the seropositivity rates and the GMTs for all 3 types of poliovirus were similarly high (96.5–100% and 170.3–368.8, respectively). Our findings from the NESVPD demonstrate that both the vaccination coverage and seropositivity rates for polio remained high in children after IPV introduction.

Pediatric HIV Infection and Decreased Prevalence of OPV Point Mutations Linked to Vaccine-associated Paralytic Poliomyelitis.

BackgroundMutations associated with prolonged replication of the attenuated polioviruses found in oral poliovirus vaccine (OPV) can lead to vaccine-derived poliovirus (VDPV) and cause paralysis indistinguishable from that caused by wild poliovirus. In response, the World Health Organization has initiated the transition to exclusive use of inactivated poliovirus vaccine (IPV), with OPV administration in cases of outbreak. However, it is currently unclear how IPV-only vaccination, well known to provide humoral but not mucosal immunity, will impact the development of paralysis causing OPV variants. Children infected with human immunodeficiency virus (HIV) have been documented to show decreased mucosal immunity following OPV vaccination. Thus, HIV-infected children vaccinated with OPV may serve as proxy for children with IPV-only vaccination.MethodsWe conducted a prospective study of Zimbabwean infants receiving OPV as part of their routine vaccination schedule. Stool samples collected from OPV-vaccinated children serially until age 24 months were tested for OPV serotypes using a real-time polymerase chain reaction protocol that quantifies the amount of mutant OPV variants found in each sample.ResultsOut of 2130 stool samples collected from 402 infants 365 stool samples were OPV positive: 313 from 212 HIV-noninfected (HIV−) infants and 52 from 34 HIV-infected (HIV+) infants. HIV− infants showed significantly higher proportions of OPV mutants when compared to HIV+ infants.ConclusionsHIV infection is associated with a reduced proportion of OPV vaccine associated paralytic polio mutants. These results suggest that OPV administered to individuals previously vaccinated only with IPV will show decreased propensity for OPV mutations.

Quantity of Vaccine Poliovirus Shed Determines the Titer of the Serum Neutralizing Antibody Response in Indian Children Who Received Oral Vaccine.

Replication of oral poliovirus vaccine (OPV) in the intestine (ie, vaccine take) is associated with seroconversion and protection against poliomyelitis. We used quantitative polymerase chain reaction analysis to measure vaccine shedding in 300 seronegative infants aged 6–11 months and in 218 children aged 1–4 years 7 days after administration of monovalent or bivalent OPV. We found that the quantity of shedding correlated with the magnitude of the serum neutralizing antibody response measured 21 or 28 days after vaccination. This suggests that the immune response to OPV is on a continuum, rather than an all-or-nothing phenomenon, that depends on efficient vaccine virus replication.

Live attenuated enterovirus vaccine (OPV) is not associated with islet autoimmunity in children with genetic susceptibility to type 1 diabetes: prospective cohort study.

Animal and human studies have implied that enterovirus infections may modulate the risk of islet autoimmunity and type 1 diabetes. We set out to assess whether serial administration of live oral poliovirus vaccine (OPV) in early life can influence the initiation of islet autoimmunity in a cohort of genetically predisposed children. OPV was administered to 64 children and a further 251 children received inactivated poliovirus vaccine (IPV). The emergence of type 1 diabetes-associated autoantibodies in serum (autoantibodies to GAD, insulinoma-associated protein 2, insulin and islet cells) was monitored during prospective follow-up. Stool and serum samples were collected for enterovirus detection by RT-PCR. Administration of OPV increased enterovirus detected in stool samples from 11.3% to 38.9% (p<0.001) during the first year of life. During the follow-up (median 11.0years), at least one autoantibody was detected in 17.2% of children vaccinated with OPV and 19.1% with IPV (p=0.723). At least two autoantibodies were observed in 3.1% and 6.8% of children, respectively (p=0.384). Replication of attenuated poliovirus strains in gut mucosa is not associated with an increased risk of islet autoimmunity. ClinicalTrials.gov : NCT02961595.

Interference of Monovalent, Bivalent, and Trivalent Oral Poliovirus Vaccines on Monovalent Rotavirus Vaccine Immunogenicity in Rural Bangladesh.

Trivalent oral poliovirus vaccine (OPV) is known to interfere with monovalent rotavirus vaccine (RV1) immunogenicity. The interference caused by bivalent and monovalent OPV formulations, which will be increasingly used globally in coming years, has not been examined. We conducted a post hoc analysis to assess the effect of coadministration of different OPV formulations on RV1 immunogenicity. Healthy infants in Matlab, Bangladesh, were randomized to receive 3 doses of monovalent OPV type 1 or bivalent OPV types 1 and 3 at either 6, 8, and 10 or 6, 10, and 14 weeks of age or trivalent OPV at 6, 10, and 14 weeks of age. All infants received 2 doses of RV1 at about 6 and 10 weeks of age. Concomitant administration was defined as RV1 and OPV given on the same day; staggered administration as RV1 and OPV given ≥1 day apart. Rotavirus seroconversion was defined as a 4-fold rise in immunoglobulin A titer from before the first RV1 dose to ≥3 weeks after the second RV1 dose. There were no significant differences in baseline RV1 immunogenicity among the 409 infants included in the final analysis. Infants who received RV1 and OPV concomitantly, regardless of OPV formulation, were less likely to seroconvert (47%; 95% confidence interval, 39%-54%) than those who received both vaccines staggered ≥1 day (63%; 57%-70%; P < .001). For staggered administration, we found no evidence that the interval between RV1 and OPV administration affected RV1 immunogenicity. Coadministration of monovalent, bivalent, or trivalent OPV seems to lower RV1 immunogenicity. NCT01633216.

Nearly Constant Shedding of Diverse Enteric Viruses by Two Healthy Infants

Stool samples from two healthy infant siblings collected at about weekly intervals during their first year of life were analyzed by PCR for 15 different enteric viral genera. Adenovirus, Aichi virus, Anellovirus, Astrovirus, Bocavirus, Enterovirus, Parechovirus, Picobirnavirus, and Rotavirus were detected. Not detected were Coronavirus, Cardiovirus, Cosavirus, Salivirus, Sapovirus, and Norovirus. Long-term virus shedding, lasting from one to 12 months, was observed for adenoviruses, anelloviruses, bocaviruses, enteroviruses, parechoviruses, and picobirnaviruses. Repeated administration of oral poliovirus vaccine resulted in progressively shorter periods of poliovirus detection. Four nonpolio enterovirus genotypes were also detected. An average of 1.8 distinct human viruses were found per time point. Ninety-two percent (66/72) of the fecal samples tested contained one to five different human viruses. Two British siblings in the mid-1980s showed nearly constant fecal viral shedding. Our results demonstrate that frequent enteric infections with diverse viruses occur during early childhood in the absence of severe clinical symptoms.

Recurrent isolation of poliovirus 3 strains with chimeric capsid protein Vp1 suggests a recombination hot-spot site in Vp1

Five oral poliovirus vaccine (OPV) strains carrying an intertypic PV3/PV2 recombination in VP1 capsid protein were isolated during poliovirus surveillance. These five PV3 strains had altogether four diverse recombination crossover points near the 3′ end of the VP1 coding region. The complete antigenic site IIIa was replaced by PV2-specific amino acids in four of the studied PV3 strains. Low overall number of nucleotide substitutions in VP1 indicated that the predicted replication time, “age”, of the PV3 strains was short, 6 months or less. The nucleotide 472-T in the 5′ non-coding region, associated to the attenuated phenotype of PV3/Sabin, was reverted to wild-type C in all studied PV3/PV2 recombinant strains. Three of the PV3 strains had at least a tripartite genome deduced from the partial 3D polymerase-coding region sequences. Our results suggest that there exists a PV3/PV2 recombination hot-spot site in the 3′ partial region of the VP1 capsid protein and that the recombination may occur within weeks or a few months after the administration of OPV.

Assessment of a two-dose administration of oral poliovirus vaccine for virulent vaccine-derived polioviruses

Assessment of a two-dose administration of oral poliovirus vaccine for virulent vaccine-derived polioviruses

Complete genomic characterization of an intertypic Sabin 3/Sabin 2 capsid recombinant

The genetic properties of strain K/2002, isolated from fecal samples of a 7-month-old child who had received his first oral poliovirus vaccine (OPV) dose at the age of 3 months, are described. Preliminary sequencing characterization of isolate K/2002 revealed an S3/S2 recombination event at the 3' end of the VP1 coding region. A recombination event resulted in the introduction of six Sabin 2 amino acid residues in a Sabin 3 genomic background. Furthermore, mutations associated with loss of the attenuated phenotype of Sabin 3 strains have been identified in the genome of isolate K/2002. The data presented here emphasize the need for careful planning of vaccination strategies, which involve stopping OPV administration in regions that are certified to be polio-free.

Analysis of Reversions in the 5′‐Untranslated Region of Attenuated Poliovirus after Sequential Administration of Inactivated and Oral Poliovirus Vaccines

Replication of Sabin strains used in oral poliovirus vaccine (OPV) in the intestines of vaccine recipients leads to reversions that increase virus neurovirulence. Previously, a small study reported that prior immunization with inactivated poliovirus vaccine (IPV) resulted in faster accumulation of revertant virus, thus potentially increasing the risk of vaccine-associated paralytic poliomyelitis. We studied the impact that prior immunization with IPV and OPV has on shedding of revertant virus by healthy infants. By polymerase chain reaction (PCR), we amplified full-length poliovirus genomes directly from stool specimens from unimmunized infants and from infants previously immunized with IPV or OPV. The amplicons were used to quantify reversions in the 5'-untranslated region, using oligonucleotide microarray hybridization. Nearly all 140 samples that were PCR positive contained varying amounts of revertants of all 3 poliovirus serotypes. Polioviruses of Sabin types 2 and 3 reverted more easily than those of type 1. Prior vaccination with IPV did not increase the proportion of revertants after OPV administration.

Evolution of a rare vaccine-derived multirecombinant poliovirus

Recombination is one of the mechanisms by which viral genomes evolve. A vaccine-derived multirecombinant poliovirus strain was isolated from a 5-month-old child with vaccine-associated paralytic poliomyelitis after oral poliovirus vaccine administration. The isolate had an S2/S1/S2/S1 primary genomic structure as revealed by restriction fragment length polymorphism and sequencing analysis. Recombination of the middle S1/S2 region is extremely rare and one of the few characterized types of recombination with Sabin type 1 as a 5' partner. An attempt was made to perform evolutionary analysis of the contributing sequences using the identified mutations in comparison with the original Sabin sequences. A hypothesis is proposed for the order in which the identified recombination events occurred.

Shedding of sabin poliovirus Type 3 containing the nucleotide 472 uracil-to-cytosine point mutation after administration of oral poliovirus vaccine.

A uracil-to-cytosine point mutation at nucleotide (nt) 472 of Sabin oral poliovirus vaccine (OPV) type 3 is found in conjunction with vaccine-associated paralytic poliomyelitis (VAPP). Direct RNA extraction and mutant analysis by polymerase chain reaction and restriction enzyme cleavage were used to identify this point mutation in clinical samples. A total of 238 stool samples were obtained from 28 healthy infants for 6 weeks after OPV vaccination. More than 25% of infants shed OPV3 in the week after vaccination, with a decrease on day 6. A second wave of OPV3 shedding occurred beginning the second week after vaccination and was maintained through the end of the study period. During the first week after vaccination, the proportion of nt 472 mutants in the shed OPV3 increased from undetectable to almost 100%. During the second shedding period, the proportion of nt 472 mutants remained close to 100%. These results suggest that selective mutation drives the VAPP-associated nt 472 point mutation for OPV3 in the human gastrointestinal tract.

Surveillance for poliovirus vaccine adverse events, 1991 to 1998: impact of a sequential vaccination schedule of inactivated poliovirus vaccine followed by oral poliovirus vaccine.

The elimination of wild-virus-associated poliomyelitis in the Western Hemisphere in 1991 and rapid progress in global polio eradication efforts changed the risk-benefit ratio associated with the exclusive use of oral poliovirus vaccine (OPV) for routine immunization. These changes, plus the November 1987 development of an enhanced-potency inactivated poliovirus vaccine (IPV), which poses no risk of vaccine-associated paralytic poliomyelitis (VAPP), resulted in a change in polio immunization policy in the United States. In September 1996, the Centers for Disease Control and Prevention recommended that IPV replace OPV for the first 2 doses in a sequential poliovirus vaccine schedule. The Vaccine Adverse Event Reporting System (VAERS), a passive surveillance system for adverse events after receipt of any US-licensed vaccine, is used to monitor postlicensure vaccine safety. Postlicensure surveillance of vaccines is important to identify new, rare, or delayed-onset adverse reactions not detected in prelicensure clinical trials or when new vaccine schedules are adopted. Through continual monitoring of adverse events and identification of potential vaccine risks, VAERS can serve as an important resource to ensure continued public acceptance of vaccines. We compared VAERS reports after the receipt of IPV to reports after OPV in infants from 1991 through 1998. Comparisons included reports listing IPV and OPV coadministered with other vaccines. Annual reporting rates per 100 000 doses distributed within 3 severity categories (fatal, nonfatal serious, less serious) were examined. Distributions of severity categories by vaccine type, age, and time period (pre- and postrecommendation) were constructed. Safety profiles (distribution of 21 symptom groupings) for IPV and OPV reports were compared. Analysis was restricted to reports for infants 1 to 3 months old and 4 to 6 months old, corresponding generally to first- and second-dose recipients. Any notable increase in a severity or safety category for IPV compared with OPV was followed up by examining the frequency of specific symptoms, reporting source, and date of vaccination. An important limitation of VAERS is that reports do not necessarily represent adverse events caused by vaccines. In many cases, the events are temporal associations only. The annual rates of VAERS reports per 100 000 vaccine doses distributed by severity category, 1991 to 1998, were in general similar for reports after IPV compared with those after OPV. The reporting rates for poliovirus vaccine did not increase materially with the shift to IPV usage. The relative frequencies of symptoms in the fatal and nonfatal serious categories for 1998 vaccine administrations were similar to 1997 reports. Severity profiles for IPV and OPV reports in infants 1 to 3 months old and 4 to 6 months old, corresponding to first- and second-dose recipients, were remarkably similar. The frequency of symptoms listed on IPV reports categorized as fatal or serious was examined by age, vaccine combinations, and time period, and the distribution of symptoms was similar for ages 1 to 3 months and 4 to 6 months. In the postrecommendation period, the 10 most frequent symptoms reported with IPV were also reported with OPV in either similar or lower relative frequency. During the postrecommendation period, safety profiles for infants 4 to 6 months old showed a 2.5% higher proportion in the allergic reaction category for IPV than for OPV, but none of the allergic reaction reports indicated anaphylaxis. In general, the distribution of symptom groupings was not markedly different for IPV compared with OPV. No cases of VAPP were reported after the administration of IPV, whereas 5 VAPP cases were reported after the administration of OPV. Although VAERS is subject to the limitations of most passive surveillance systems, the large number of reports and national coverage provide a unique database for monitoring vaccine safety. There was a marked increase of IPV reports in VAERS after 1996, consistent with implementation of the Advisory Committee on Immunization Practices recommendation for the sequential IPV/OPV poliovirus vaccination schedule. Given the increased use of IPV, a review of potential adverse events in VAERS compared IPV with OPV reports both before and after the introduction of the sequential vaccination schedule. Vaccine safety surveillance indicated no adverse events patterns of potential concern following the use of IPV in infants after the introduction of the sequential vaccination schedule. Ongoing surveillance is documenting a decrease in VAPP. These findings provide useful information to support the Advisory Committee on Immunization Practices recommendation, made in 1999, to shift to an all-IPV schedule.

Nationwide oral poliovirus vaccination campaign and the incidence of Guillain-Barré Syndrome.

A retrospective analysis of the incidence of Guillain-Barré syndrome (GBS) in Finland in 1981-1986 was carried out by careful examination of medical records identified from nationwide Hospital Discharge Register data based on a mean total population of 5 million people. Records from 247 patients fulfilled the accepted criteria of GBS corresponding to a mean annual incidence of 0.82 per 100,000 population. Monthly rates showed an increased incidence of GBS in March 1985, following by a few weeks the onset of the nationwide oral poliovirus vaccine campaign and partly overlapping it. Analysis of the time series in depth suggested, however, that a change point in the occurrence of GBS had already taken place before the oral poliovirus vaccine campaign. Widespread circulation of wild-type 3 poliovirus in the population immediately preceded the oral poliovirus vaccine campaign and the peak occurrence of GBS. These results demonstrate a temporal association between poliovirus infection, caused by either wild virus or live attenuated vaccine, and an episode of increased occurrence of GBS, but they cannot prove the suspected cause-effect relation between GBS and oral poliovirus vaccine administration.

Thermostabilization of live virus vaccines by heavy water (D 2O)

Eradication of poliomyelitis is based on the mass administration of oral poliovirus vaccine (OPV). Delivery of effective vaccines in the developing world, especially in tropical areas, is compromised when refrigeration cannot be assured. The OPV, prepared with three live attenuated polioviruses (Sabin strains, serotypes 1, 2 and 3), is considered to be the most thermolabile of vaccines in the World Health Organization's Expanded Programme on Immunization. To be effective, the initial concentration (potency) of each of the three component serotypes, measured in tissue culture infective doses, should not decrease by more than 0.5 log 10 before vaccine delivery. High concentration (1 M) of MgCl 2 is currently used as stabilizer for OPV. The stabilizing effect of D 2O was tested here on OPV strains. By diluting the viral suspension with D 2O-based salt and buffer solutions, in a manner similar to that involved in OPV production, an 87% concentration of D 2O in the final viral preparation was achieved. In severe conditions of testing (incubation for 3 days at 45°C), the Sabin 3 virus lost an average of 2.7 log 10 potency in the presence of 87% D 2O as compared to 3.0 log 10 in H 2O-based 1 M MgCl 2, and to 5.7 log 10 in the H 2O-based control solutions. When tested in a combined 87% D 2O and 1 M MgCl 2 treatment, the Sabin 3 virus lost only 1.3 log 10 potency after 3 days at 45°C. Similar thermostabilizing effects were obtained for Sabin 1 and Sabin 2 strains, but the level of stabilization was slightly lower. Tested in standard conditions at 37°C for 7 days, the infectivity of the three D 2O MgCl 2-treated OPV strains remained in the limit of requirements (≤0.5 log 10). The stabilizing effect of D 2O was also demonstrated on yellow fever 17D vaccine virus strain. D 2O, alone or in combination with other stabilizers such as MgCl 2, could thus be considered as a candidate for the improvement of live virus vaccine thermostability.

Oral polio vaccination during pregnancy: no increase in the occurrence of congenital malformations.

To examine the possible association between maternal vaccination with oral polio-virus and congenital malformations of the child, use was made of a nationwide mass vaccination in Finland. During a restricted period in 1985, a vaccination with trivalent oral poliovirus was implemented with coverage of 94% of the population. The study population was chosen from three major hospitals in the Greater Helsinki Region in Finland which deliver over 95% of the children of their catchment area. One study and two reference cohorts were delineated; the former consisted of pregnancies that were in their first trimester during the vaccination period. The two reference cohorts included mothers from the same hospitals whose pregnancies were likewise in the first trimester during the corresponding time period in 1984 and 1986, i.e., 12 months before and after the study period. Each cohort consisted of approximately 3,000 mothers/children whose delivery and hospital records were manually perused by trained nurses. All the structural malformations reflecting an impaired organogenesis during the sensitive first trimester were monitored. A total of 209 (2.3%) such malformations were recorded and characterized. There were no differences between the study and reference cohorts (risk ratio = 0.7, 95% confidence interval 0.5-1.0). According to the authors' power estimate, an additional prevalence greater than 0.5% would have been detected. The authors conclude that administration of oral poliovirus vaccine during early pregnancy was not associated with an elevated risk of congenital malformations.

1963 Epidemic of Poliomyelitis in Barbados, West Indies

FROM MARCH 23 through June 19, 1963, 68 cases of paralytic poliomyelitis were noted on the island of Barbados among a population of 232,333, an attack rate of 29.3 per 100,000, and a dramatic increase from the annual totals of 0-7 cases recorded during the period 1952-62 (unpublished data, M.A.B.). Indeed, the only previous significant outbreak of poliomyelitis had occurred in 1933 and totaled 61 cases concentrated in the 0-5-year age group (1). During the 1963 epidemic in this circumscribed population, careful epidemiologic olbservations showed abrupt termination of the outbreak temporally related to the mass islandwide administration of oral poliovirus vaccine. The epidemiologic features of t.he outbreak, particularly as related to the attempted control measures, will be discussed in some detail.

Inclusion-bearing Cells in the Urine. - Studies on Poliomyelitis, Acute Myelocytic Leukemia and the Administration of Oral Poliovirus Vaccine

Inclusion-bearing Cells in the Urine. - Studies on Poliomyelitis, Acute Myelocytic Leukemia and the Administration of Oral Poliovirus Vaccine